The present invention relates generally to an apparatus for driving elevator doors and, in particular, to a door drive apparatus with a door locking mechanism.
It is well known to provide an elevator car with a door drive apparatus to open and close the car door and the elevator shaft door at a floor. The door drive apparatus can include a shaft door coupling mechanism including an entraining parallelogram linkage mounted on a car door section and two coupling rollers positioned at each shaft door. A drive means mounted above the car door drives an actuating lever which is coupled to the linkage to move the car door between the closed and the open positions. A locking mechanism includes a pivotably mounted car door bolt which is monitored by a safety contact, is arrestable at an abutment, is locked by its own weight in a retaining position and which is urgeable into a releasing position by a control roller running up onto a control cam.
A door drive apparatus of the type described above is shown in Swiss Pat. No. 663,406, in which the shaft door is moved with the car door of an elevator car situated in the door opening zone of a floor. The doors are lockingly connected with each other by an entraining parallelogram linkage which is mounted on the car door and is movable by two entraining members mounted on the shaft door. A pivotably attached car door bolt is mounted on the car door and is locked by its own weight at an abutment on the car. In the door opening zone of a target floor, the bolt is unlocked by the running up of a first control roller, which is positioned adjacent an angle lever articulatedly connected with the bolt, onto a control cam positioned at each floor, wherein the coupled doors in normal operation are automatically opened and again closed by the door drive apparatus.
In the case of a power failure, the car door remains locked outside the door opening zone. In the door opening zone, the entraining parallelogram linkage is drawn apart by the force of a tension spring, wherein the door drive apparatus is guided out of a dead center position with the aid of a double lever and a second control roller. Also, the locked car door is unlocked by the impinging of the first control roller on the control cam at the floor and the movement connected therewith of the angle lever and the articulated bolt. The car door and the coupled shaft door then can be opened by hand.
A disadvantage of this apparatus is that a control cam for the unlocking of the car door is required at each floor, which control cam must cooperate exactly at each floor with the drive apparatus mounted on the car and therefore requires exact and expensive installation at the building site. A further disadvantage is that the entraining parallelogram linkage in the open position can be compressed by external forces or inertia forces, whereby disturbing noises are generated.